Warning: Unexpected character in input: '\' (ASCII=92) state=1 in
.../plugins/tinymce4/admin.php on line 168
Parse error: syntax error, unexpected T_STRING in .../plugins/tinymce4/admin.php on line 168

While this may prevent the parse error, it certainly won't work as expected. The backslash is correct here, though it requires at least PHP 5.3. Apparently, you're using an older PHP version (5.2?) If you can't upgrade (what would be preferable), I suggest you stick with TinyMCE 3 (i.e. tinymce) as editor for now.

While this may prevent the parse error, it certainly won't work as expected. The backslash is correct here, though it requires at least PHP 5.3. Apparently, you're using an older PHP version (5.2?) If you can't upgrade (what would be preferable), I suggest you stick with TinyMCE 3 (i.e. tinymce) as editor for now.

One site have PHP Version 5.2.17 (Build Date Mar 25 2015) and second PHP Version 5.6.17 (Build Date Jan 31 2016) .